Adjustable reamer



w. c. BROGA ADJUSTABLE VREAMER Filed July 4, 1942 Fig.1

Oct. 31, 1944.

3mm Wile an E3- Eirmga .blades in this manner.

Patented Oct. 31, 1944' UNITED STATES PATENT OFFICE ADJUSTABLE REALIE-R Wilson 0. Broga, Westfleld, Mass..

Application July 4, 1942, Serial No. 449,809

(Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) 1 Claim.

This invention relates to an adjustable reamer and particularly to an improved. construction thereof permitting the grinding of the blades of such reamer for sharpening purposes by -a parallel axis rotating wheel grinder without removal of the blades from thereamer.

Adjustable reamers generally comprise a shank or body member having longitudinal slots therein in which the cutting blades of the reamer are inserted and supported. After; the cutting blades'are worn and reground to an extent that the reamer is no longer satisfactory for the desired work diameter then it is only necessary to insert new blades in the shank to bring the reamer back to its original working diameter. This results in aconsiderable saving of tool steel over the amount required for the one-piece reamer which must be discarded inits entirety after extensive wear.

The regrinding of any reamer, adjustable or integral, has been a careful and time-consuming procedure. It is necessary to grind the external surface of the reamer blade to a slightly smaller radius than the. actual radius of the leading or cutting edge of such surface in order to provide the necessary angle of relief between the blade surface and the work surface. Such angle heretofore could be produced only by vgrinding along the longitudinal axis of the greatly reduced the quality and efliciency of its performance. Furthermore, a skilled operator was required in order to regrind the reamer In connection with adjustable reamers, there have been methods devlsed wherein the reamer blades. may be accurately ground, but'this involved the removal of the reamer blades from the reamer shank for the grinding operation and accordingly increased the amount of time consumed in the grinding operation.

It is accordingly an object of this invention to produce an improved adjustable reamer which may be reground in much less time and with a much higher degree of accuracy than possible with conventional reamer constructions.

A further object of this invention is to produce an adjustabl reamer wherein all necessary grinding of the reamer surfaces may be accomplished without removal of the cutting blades from the reamer.

It is a. particular object of this invention to produce an adjustable reamer wherein the grinding of a cutting surface to a desired angle of relief may be accomplished with any desired degree of accuracy by radial grinding, i. e., with the axis of the grinding wheel parallel to the axis of the reamer.

The specific nature of the invention as well as other objects and advantages thereof will clearly appear from a description of a preferred embodiment as shown in the accompanying drawing in which- Fig. 1 is a side elevational view shown partly in longitudinal section of an adjustable reamer.

Fig. 2 is a right end elevational view of the reamer shown in Fig. 1.

Fig. 3 is a cross sectional. view taken along the plane 3-3 of Fig. 1.

Fig. 4 is a cross sectional view taken along the plane 4-4 of Fig. 1. v

Fig. 5 is across sectional view of the reamer shown in Fig. 1 taken along the plane 4-4 show-- ing an'alternate form of securing the cutting blades to the body of the reamer.

As shown in assembled relation in Fig. 1, the

reamer comprises a shank I, one end la of whichmay be engaged by, the tool holder of any suitdisposed with respect to the radii of the shank,

as best shown in Figs. 2 'to 5. The slots lc extend throughout the length of the threaded portion lb of the shank I. I

The depth of the slots lc varies along the axis of the reamer shank l. Beginning at the left-hand end of the threaded portion of the shankl, as shown in Fig. 1, the slots increase in depth uniformly along the axis of the shank.

A reamer blade 2 is fitted snugly into each of the slots lc but the fit is suiliciently loose to permil; the blades to be freely moved throughout the slots. The blades 2 are securely held in any desired position within their respective slotsby any convenient means such as nut members 3 and 4 which are screwed upon the shank threads lb on each side of the blades 2. The nut members 3 and 4 each have an overhanging axial extension 5 and 6 respectively on their sides adjacent the blades 2., The surfaces of contact between the blades 2 and the nut extensions 5 and 6 are inclined as respectively shown at 5a and 6a. Accordingly the blades 2 will be securely held Within the slots Ic regardless of whether they are located in the shallow or deep portion of such slots.

An alternative method of securing the reamer blades 2 in the slots I is illustrated in Fig. 5. In this construction, the slots Ic are constructed as inverted-T slots and the bases of the reamer blades 2 are correspondingly shaped as indicated at 20. 3 and 4 are still necessary in order to secure the blades 2 in a fixed position in the shank I, but the overhanging extensions 5 and 6 on the nut members 3 and 4 may be eliminated since any radial movement of the blades 2 out of the slots I0 is prevented by the T-shape.

The grinding of an adjustable reamer of either of the described constructions proceeds as follows: The reamer is centered in any suitable grinding machine (not shown) on the centers Id and le in the shank I. The blades 2 are inserted in the slots I0 and positioned in the right-hand end portion of the slots Ic as viewed in Fig. 1. The blades are secured in this position by tightening of the nuts 3 and 4. A rotating-wheel grinder (not shown) having its axis parallel to the reamer axis is then applied to the blade and the external surfaces 2a of the blade 2 ground to a curvature having a radius equivalent to the distance from the surfaces 2a to the center of the shank I, when the blades are in the grinding position; It is necessary of course to rotate or rock the reamer on its centers Id and Ie during the grinding.

To use the reamer on a work piece, the nuts 3 and 4 are loosened and the blades moved to the left from the grinding position and secured in the new position by tightening of the nuts 3 and 4. In such position, shown in cross section in Fig. 4, the cutting radius of the leading edge 2b of the blade surfaces 2a now has a larger radius with respect to the center of the shank I than the radius to which the surfaces 2a were ground in the grinding position. This increase in radius of the cutting edge 2b is of course produced by the radially outward movement of the blades 2 caused by the decreased depth of the slots Is in the new position of the blades 2. It is readily apparent that when the blades 2 are moved to any position in the slots Is to the left of the grinding position, as viewed in FigI 1, a relief angle will be obtained between the blade surface 2a and the work surface. The magnitude of such a relief angle will depend upon the slope of the base of the slots I0 and the distance that the blades 2 are moved in the slots to the left of the grinding position. It is apparent that if the working diameter for the reamer is known,

the slope and length of the slots Ic may be read-,

ily propo tioned to produce any desired relief angle. Furthermore the initial working position of the reamer blades 2 should be selected to be only so far to the left of the grinding position of the blades 2 as is necessary to obtain the desired angle of relief and still be to the right of the beginning of the slots Ic. With this condition, greatly increased life of the reamer blades 2 at a desired diameter may be obtained since after each successive grinding they may be moved slightly more to the left to the beginning f the slots I0 and the increased radius of the leading edge 21) thereby obtained, will compensate for the With this construction the nut members decrease in height of the reamer blades due to the grinding.

It is apparent that increased relief angles may be obtained by positioning the slots Ic at greater offset distances frornthe center of shank I. In any event the forward surfaces of the blades will be offset with respect to the radii of the body and with respect to the direction of rotation of the reamer so that a positive angle of rake is defined.

The tapered depth slot construction shown should not be construed as limiting this invention to such construction as it is obvious that the same results may be obtained with slots having stepped increases in depth.

With an adjustable reamer constructed as described, the surfaces of the reamer blades are radially ground and hence all blade surfaces will not only be exactly symmetrical but the desired radius of such surface can be accurately produced. It should be understood that a reamer of the constructions described can be readily designed for any substantial working diameter and that any desired relief angle may be obtained by merely changing the slope of the base or the length of the slots Ic.

It will be appreciated that the reamer of this invention has a positive angle of rake defined, as contrasted with a negative angle; the latter gives a partial swaging action (instead of a free cutting action) and increases the power factor and shortens the life of the cutting edges and produces an inferior surface on the work, whereas the reamer herein described, with its slots of variable depth and of offset position with respect to the radius of the shank, makes it possible to sharpen the blades by cylindrically grinding them in the deep portion of the slots. Then, according to this invention, by the single adjustment of moving the blades to the shallow portion of the slots so that the cutting edges assume the desired working diameter, a reamer is obtained.

with cutting blades having both a convex relief surface and a positive angle of rake.

I claim:

An adjustable reamer comprising in combination, a shank adapted for rotation in a certain direction and provided with a plurality of longitudinal slots therein which are equally spaced around the periphery thereof, the depth of said slots varying along the axis of the shank but being equal at any given point therealong, cutting blades fitting in said slots, the length of said blades being substantially less than the length of the slots whereby said blades may be moved from the shallow portion of said slots to the deep portion of said slots, means arranged to secure said blades in said slots in either the shallow or deep portion thereof, said slots being so offset with respect to the longitudinal axis of the shank that the forward surfaces of said cutting blades are-in a plane rearward, with respect to said direction of rotation of the shank, of a parallel plane through the axis of the shank whereby a positive angle of rake is defined, means for securing said blades in a plurality of positions along the axis of said shank, and an arcuate exterior surface on each blade formed by cylindrically grinding said blades when the latter are located in the deep portion of said slots thereby forming a positive rake cutting edge at the intersection of said arcuate surface and said forward surface 

